1. Field of the Invention
This invention relates to a buckle device for the seat belt in a vehicle.
2. Description of the Prior Art
Various types of such buckle device are known. A typical one basically comprises a push button, a latch device having a latch member pivotable by bias means operable by the push button, and a tongue adapted to be inserted into the latch device and locked by the latch member. However, the buckle devices of the prior art have offered various disadvantages in safety and ease of handling, as will hereinafter be described more specifically.
(1) It is empirically known that if the tongue inserted into and locked by the latch device is pulled with a force of approximately 2.4 tons, the tongue will be deformed and slip out. This is considered to be attributable to the fact that the great degree of inclination of the upwardly biased latch member resting on the base of the latch device tends to create a couple of forces which deforms the tongue. Such a degree of pull force may occur, for example, from a great impact exerted on a vehicle occupant when an automobile running at high speed collides against another, and this may cause the tongue to slip out to invite a danger of serious disaster. To avoid such danger, the tongue must be made bulky and this would in turn lead to a larger size of the entire buckle device.
(2) When the tongue is inserted into the latch device so as to be locked by the latch member, and when the tongue is withdrawn from the latch device by operating the push button to unlock the tongue from the latch member, the latch member biased upwardly by bias means tends to cause occurrence of the so-called false latching condition in which the tongue is pinched between the latch member and a part of the base of the latch device and becomes hardly movable. This would make the wearer of the seat belt feel worried about manipulation of the buckle device, and may lead him to believe that the tongue is completely locked by the latch member, in spite of the fact that the tongue is not completely latched. Accordingly, for example, during an emergency in which great shocks are exerted on the belt wearer, the tongue would simply slip out of the latch device, with a result that the buckle device could not achieve its intended purpose.